Chemically modified high oil asphalt

ABSTRACT

A chemically modified asphalt composition is provided which is especially adapted for use in the repair and maintenance of highways. The composition is a reaction product of a high oil asphalt, a vinyl aromatic monomer and a rubbery, or elastomeric, polymer.

This is a division of application Ser. No. 407,373, filed Aug. 12, 1982,U.S. Pat. No. 4,444,947.

CROSS REFERENCES

The present application is related to the subject matter of copendingapplication U.S. Ser. No. 359,328 and 360,729, both of which are herebyincorporated by reference.

TECHNICAL FIELD

The present invention is related to chemically modified asphalts, andmore specifically, to asphalts which are chemically modified by reactionwith a vinyl aromatic monomer and a rubbery, or elastomeric, polymer.The present invention is also related to glass fibers coated with suchchemically modified asphalt compositions and to preformed membranescomprising a fibrous reinforcement which is coated with such chemicallymodified compositions.

BACKGROUND AND SUMMARY

Chemically modified asphalts are receiving widespread commercial useespecially in the areas of highway maintenance and repair. As usedherein, the term "highway maintenance and repair" includes not only therepair and maintenance of highways and roads but also contemplates,within its scope, such structures as driveways, parking lots, airportrunways and like vehicular supporting surfaces, and also contemplates,within its scope, waterproofing of bridge decks. Exemplary of suchchemically modified asphalt compositions are those produced by reactingasphalt, a vinyl aromatic monomer and a rubbery or elastomeric polymer,as set forth example in U.S. Pat. No. 4,273,686, which is herebyincorporated by reference. Such types of compositions have been employedfor minimizing reflective cracking, for joint and crack sealingpurposes, for bridge deck waterproofing and for pothole repair. Thesecompositions may be employed as is or, if desired, glass fibers may bedispersed therein. In highway repair and maintenance, for purposes ofminimizing reflective cracking, cracks may first be filled with suchchemically modified asphalt compositions, and then the crack overlaidwith a fibrous reinforcement material, preferably a glass fiberreinforcing material, and the reinforcing material then overcoated witha hot application of such chemically modified asphalts.

While chemically modified asphalts, which are produced by reacting apaving grade asphalt, a vinyl aromatic monomer and a rubber orelastomeric polymer, have many outstanding properties making them welladapted for applications indicated above, such formulations need to beimproved with respect to their resistance to thermal degradation andwith respect to their low temperature flexural strength properties.

Compared to such chemically modified asphalts, wherein the asphaltemployed is an AC--20 paving grade asphalt, the present inventionprovides compositions which have increased resistance to thermaldegradation and improved low temperature flexural strengths, and whichcan be synthesized in a shorter period of time. That is, ingredientsemployed in the present invention generally show enhanced reactionkinetics compared to the use of an AC--20 paving grade asphalt.Essentially, the present invention is a chemically modified asphaltcomposition comprising the reaction product of a high oil asphalt, avinyl aromatic monomer and a rubbery, or elastomeric, polymer.

DESCRIPTION OF THE INVENTION

As indicated above, the present compositions are produced by reacting ahigh oil asphalt, a vinyl aromatic monomer and a rubbery, or elastomericcopolymer. The reaction is done at a temperature and time sufficient toallow the reaction to proceed. Preferably, the reaction is done byheating at a temperature of at least about 150° C. for at least about 15hours. Outstanding results will be obtained by reacting the ingredientsby heating at a temperature of about 165° C. for about 15 or 16 hours upto about 24 hours. More generally, with respect to the involved typereactions, it will be found that in plotting viscosity against time, ata given reaction temperature, a curve generally having three portionswill be obtained. Actually, there may be a fourth portion in the initialstages of the reaction where the curve will show a slight decrease inviscosity, but this is generally felt to be a dissolution phenomenon,where the system becomes more homogeneous and flowable, rather than theresult of a chemical reaction and, consequently, this early viscositychanging stage is not viewed as part of the three portion curve. Thefirst portion of the curve is characterized by a generally modestincrease in viscosity and is followed by the second portion which ismore steep than the first portion because of a more rapid increase inviscosity. This second portion is then followed by the third, orplateau, portion which is characterized by a slow, or modest, viscosityincrease. Suitably, the reaction will be conducted for a time sufficientfor the viscosity to reach the third, or plateau, portion of theviscosity-time curve. This viscosity, where the second portion of thecurve generally changes to the plateau portion of the curve, may beviewed as a plateau viscosity. Preferably, however, the reaction will beconducted for a time which is at least about 20 or 25% greater than thetime needed to reach the plateau viscosity. Times of about 1.2 to about1.5 times the time needed to reach the plateau viscosity at a givenreacting temperature produce outstanding chemically modified asphalts.While the proportions of ingredients may vary depending on the specificapplication employed, quite outstanding compositions will be obtainedwhen the vinyl aromatic monomer is employed in an amount of about 7 to20% by weight based on the asphalt, and the rubbery, or elastomericpolymer, is used in an amount ranging from about 5 to about 14% byweight based on the weight of the asphalt.

The high oil asphalts employed in the present invention are not pavinggrade asphalts but are more in the nature of what is recognized in theroofing industry as a blown roofer's flux. Approximately 20% of theasphalt produced currently would be considered high oil asphalt. Highoil asphalt is residual from a refining tower, either vacuum or gravity,which has a low asphaltene content, e.g. less than about 25% (weight),and a high combined naphthene and polar aromatic content, e.g. greaterthan about 40%, which residue is air blown to produce an asphalt with ahigh penetration (at 77° F.) to softening the point ratio. Desirably,the penetration to softening point ratio will be about 0.385 with apenetration of at least about 50 and a softening point of, for example,about 130° F. Air blowing of, for example, Union Oil VTB asphalt toproduce an asphalt which has a softening point of about 130° F. (54°C.), a penetration at 77° F. of about 60, a flashpoint of about 580° F.(304° C.) and a Brookfield viscosity at 400° F. (204° C.) of about 40cps exemplifies a specific suitable material. Desirably, the high oilasphalts employed in the present invention have a dimensionlessviscosity factor of at least about 120 and more suitably about 125-135.This viscosity factor is calculated according to the formula:

    A/B×log A/log B

where A is the viscosity of the asphalt at 200° F. and B is theviscosity of the same asphalt at 325° F. AC--20 asphalts, for example,have viscosity factors of less than about 100 and typically about 85-95.Generally, the high oil asphalts employed herein will have a viscosityof about 550 cps to about 700 cps at 260° F.

The polymerizable vinyl aromatic monomer preferably will be one of thegeneral formula (R₁) (R₂) C=C (R₂) (R₃), wherein R₁ is an aromatic groupcontaining six to 12 carbon atoms, including a phenol group, asubstituted phenol group, wherein the substituant is any one of a cyanogroup, a hologen group, a C1 to C3 alkyl group, a hydroxy group, a nitrogroup, etc.. R₂ is preferably hydrogen or a lower alkyl, e.g. a C₁ to C₅alkyl such as methyl and R₃ is hydrogen or such lower alkyl.

As the rubbery, or elastomeric, polymer, use can be made of a number ofnon-depolymerized elastomeric materials which are homopolymers of aconjugated diene (for example, butadiene isoprene, chloroprene) and moregenerally, a conjugated diene having about 4 to 6 carbon atoms, or acopolymer of such conjugated dienes with at least one ethylenic monomercopolymerizable therewith, such as, for example, styrene, acrylonitrile,methocrylonitile.

Such nondepolymerized polymers are widely available commercially withthe suitable polymers being a copolymer of styrene and butadiene such asthat marketed by Phillips Petroleum as their Solprene 1205C elastomer.

In addition to the uses described above for highway repair andmaintenance purposes, the present compositions can also be employed informing preformed membranes for such uses. Preformed membranes for suchpurposes are known in the art and generally comprise a fibrousreinforcement material having an asphaltic coating thereon. Generally,one side of such membranes will also include a pressure sensitiveadhesive which is adapted to adhesively secure the membrane to thesupporting surface, such as, for example, a cementitous surface likeasphalt or concrete.

While the foregoing describes the present invention with sufficientparticularity to enable those skilled in the art to make and use thepresent invention, nonetheless, there follows a nonlimiting examplethereof. The high oil asphalt was prepared by air blowing a towerresidue having an asphaltene content of less than about 25% and acombined naphthene and polar aromatic content in excess of about 40%(Union Oil VTB asphalt) to a penetration of about 60 and a softeningpoint of about 130° F. (penetration to softening point ratio of about0.46). This material had a viscosity factor of about 125-135 and aviscosity at 260° F. of about 550-700 cps.

EXAMPLE I

A chemically modified asphalt was prepared from a batch of 77.6% byweight of the above high oil asphalt, 10% by weight of styrene and 12.5%by weight of a copolymer of styrene and butadiene (Solprene 1205Ccopolymer). The chemically modified asphalt was prepared in a reactorequipped with an agitator and reflux condenser by first heating theasphalt to melt it and then, with mixing and charging the styrene andstyrene-butadiene copolymer thereto followed by heating at a temperatureof about 165° C. The time of reaction was varied between about 16-24hours.

The above composition was compared to chemically modified asphaltssimilarly prepared but employing an AC--20 paving grade asphalt insteadof the high oil asphalt. AC--20 asphalt has a penetration of 42-65 and asoftening point of about 122° F.-127° F. with the higher penetrationcorrelating to the lower softening point. The AC--20 asphalt had aviscosity factor of 85-95.

Samples of these two types of chemically modified asphalts were thensubmitted to a viscosity recovery test. In this test, samples areinitially heated to a reference temperature, for example, 380° F. andheld there for a prescribed period of time, for example five minutes,then heated to another temperature, for example, 480° F. and held therefor a prescribed period of time, after which time that sample would theneither be cooled down to the reference temperature, for example, 380° F.or in some instances, heated to another temperature, for example, 500°F. held at that temperature level for a prescribed time and then againcooled down to the reference temperature. The viscosity recovery, (theinitial viscosity at the reference temperature divided into theviscosity of the material after it had been heated to highertemperatures and then cooled down again to the reference temperature)was significantly higher for the chemically modified asphalt producedfrom the high oil asphalt than that produced from an AC--20 paving gradeasphalt. This ratio of the viscosity after heat cycling to the initialviscosity indicates that the chemically modified asphalt produced fromthe high oil asphalt is more resistant to thermal degradation than isthe chemically modified asphalt made from an AC--20 paving gradeasphalt.

Additionally, the chemically modified asphalts manufactured from thehigh oil asphalt and an AC--20 asphalt were compared for their lowtemperature flexural strengths. This was done by making films of therespective materials, for example, films having a thickness on the orderof about 0.125 inches and then bending these films over a 1" mandrel.Unsatisfactory flexural strengths were qualitatively determined by theoccurrence of crazing and cracks. The chemically modified asphaltmanufactured from the high oil asphalt showed good flexural strengthproperties at about -35° F., whereas the chemically modified asphaltmanufactured from an AC--20 asphalt showed satisfactory flexuralstrengths down to about -8° F.

Additionally, the chemically modified asphalt manufactured from the highoil asphalt shows a significantly less tacky surface and is firmer inthat it has increased resistance to deformation than the chemicallymodified asphalt produced from an AC--20 asphalt.

It has also been observed that the reaction rate using high oil asphaltsis higher than that using an AC--20 asphalt. As will be readily apparentto those skilled in the art, since the chemically modified asphalts ofthe present invention exhibit greater viscosity recovery, it will beapparent that they will be more reliable for use in the field,especially in those instances where the material is applied hot, whichrequires heating in tar kettles, or asphalt melters. Thus, ifoverheating is effected, there will be a significantly better return tothe desired viscosity, and since the compositions of the presentinvention have increased resistance to thermal degradation, adverseconsequences of such degradation will be greatly minimized.

INDUSTRIAL EXPLOITATION

The compositions of the present invention may be industrially exploitedby employing them as hot applications for purposes of highway repair andmaintenance, such as, for example, in suppressing reflection cracking,crack sealing, bridge deck waterproofing and pothole repair. Insuppressing reflection cracking, the materials will be employed by firstfilling the crack with an appropriate asphaltic-based material, forexample, the present compositions, then overlaying the filled crack witha fibrous reinforcement material, such as, for example, a glass fiberreinforcement like a woven roving, and then overcoating the fibrousreinforcement with a hot application of the compositions of the presentinvention. Because of the improved resistance to thermal degradation,the materials of the present invention may be applied over a widetemperature range and will be effective over a wide ambient temperaturerange because of the improved low temperature flexural strengths ofthese compositions. These compositions are well adapted for forminglaminates, for use in highway repair and maintenance, of the type setforth in the incorporated applications.

While the above describes the present invention, it will, of course, beapparent that modifications are possible which, pursuant to the patentstatute and laws, do not depart from the spirit and scope thereof.

We claim:
 1. Glass fibers having an asphaltic coating which comprises anasphaltic-based composition which comprises the reaction product of ahigh oil asphalt, a vinyl aromatic monomer and a homopolymer of aconjugated diene or a copolymer of a conjugated diene with at least oneethylenic monomer copolymerizable therewith, said asphalt being an airblown high oil asphalt having a viscosity factor of greater than about120.